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Generation of periodic stochastic foam models for numerical analysis
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0002-9207-3404
2014 (English)In: Journal of cellular plastics (Print), ISSN 0021-955X, E-ISSN 1530-7999, Vol. 50, no 1, 37-54 p.Article in journal (Refereed) Published
Abstract [en]

Stochastic cellular models of rigid foam based on Voronoi spatial partitioning are generated and investigated for potential use in numerical analysis using finite element methods. Such partitions are deterministic once a distribution of cell nuclei has been defined. A drawback is that the models tend to exhibit a significant share of short edges and small faces. Such small geometrical features are not likely to occur in real foams since they are unfavorable from a surface energy point of view and they also generate problems in numerical analysis due to associated meshing challenges. Through minimization of the surface area, using the computer software Surface Evolver, the Voronoi models are brought to better resemblance with ideal dry foam and the occurrence of small geometrical features is strongly reduced. It is generally seen that different seed point distribution algorithms result in different model topologies. The presented methodology is systematic, parameterized and the results are very promising. Good grounds are provided for modeling of real rigid foam materials, that do not necessarily fully resemble ideal dry foam.

Place, publisher, year, edition, pages
Sage, 2014. Vol. 50, no 1, 37-54 p.
Keyword [en]
cellular, micro structure, simulation, structural foams
National Category
Aerospace Engineering Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-136575DOI: 10.1177/0021955X13503848ISI: 000328696900002Scopus ID: 2-s2.0-84890938110OAI: oai:DiVA.org:kth-136575DiVA: diva2:676496
Funder
Swedish Research Council, 50576001
Note

QC 20140124. Updated from accepted to published.

Available from: 2013-12-06 Created: 2013-12-06 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Modeling of rigid foams
Open this publication in new window or tab >>Modeling of rigid foams
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The morphology and elastic properties of foams are investigated using models accounting for the cellular structure. Different modeling approaches are evaluated and compared to the cellular structures of real foams. The aim is to find an approach that produces realistic models that can be adjusted to match morphology measures taken form real foams. The elastic properties are computed using finite element analysis and the results are compared with both experimental results from mechanical testing and existing analytical models. A generalization of the existing analytical models is suggested for better agreement with the modeling results.

In Paper A Voronoi and equilibrium foam models are generated and investigated. The Voronoi models are found to have a high content of short edges and small faces while conversion into equilibrium foams eliminates such small geometrical features. It is also seen that different seed point distribution algorithms generally result in different model topologies.

In Paper B the relations between the sphere packing fraction and the resulting degree of volumetric polydispersity are studied as well as the relations between polydispersity and a number of morphology parameters. Both Voronoi and equilibrium foams are investigated and compared with data from real foams. Such comparisons indicate that the used method is somewhat limited in terms of polydispersity but provides a controlled way of varying the foam morphology.

In Paper C equilibrium models are used to study the inuence of polydispersity, relative density and distribution of solid on the elastic properties of foams. It is found that the elastic moduli are very weakly coupled to the polydispersity while the inuence from the relative density and distribution of solid is considerably stronger. Existing analytical models from the literature are fitted to the results and generalizations are suggested for better agreement over the investigated range of relative density and distribution of solid.

In Paper D equilibrium foam models with prescribed polydispersity are generated, analyzed and compared to real foams. The polydispersity of real foams is measured in micro-CT images and the results are applied to the models. The elastic properties are computed and the results are compared with experimental results and previous models with significantly lower polydispersity. No clear relation is found between the elastic properties and the polydispersity of equilibrium foams.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xiii, 28 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2015:21
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-166197 (URN)978-91-7595-562-9 (ISBN)
Public defence
2015-05-22, D3, Lindstedtsvägen 5, KTH, Stockholm, 09:15 (English)
Opponent
Supervisors
Note

QC 20150505

Available from: 2015-05-05 Created: 2015-05-05 Last updated: 2015-05-05Bibliographically approved

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Hallström, Stefan

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